Surface-emitting laser device

ABSTRACT

A VCSEL device includes a polyimide having a larger thickness (d 1 ) on the surface of a semiconductor layer structure in a peripheral area  54 , which is separated from a mesapost by an annular groove  52 . The top surface of the central mesapost  30  is located at a lower position compared to the top surface of the peripheral area  54 . A structure is obtained wherein the mesapost is not contacted by a jig or probe during handling the device in the test or assembly thereof.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. application Ser. No. 11/554,973, filedOct. 31, 2006, the entire contents of this application is incorporatedherein by reference. The present divisional also claims the benefit ofpriority under 35 U.S.C. §119 of Japanese Patent Application No.2005-316946, filed on Oct. 31, 2005 and Japanese Patent Application No.2006-290223, filed on Oct. 25, 2006.

FIELD OF THE INVENTION

The present invention relates to a surface-emitting laser device havinga mesapost and a resonator structure normal to the substrate surfaceand, more particularly, to a surface-emitting laser device having asuperior reliability.

BACKGROUND ART

Vertical-cavity surface-emitting laser (VCSEL which is referred to assimply surface-emitting laser device or VCSEL device hereinafter) is asemiconductor laser device which emits laser in the directionperpendicular to the substrate surface thereof. The surface-emittinglaser device is such that a large number of VCSEL devices can bearranged in a two-dimensional array on a common substrate, and nowattracts an attention as a light source in the field of communication aswell as a specific device for a variety of applications. The VCSELdevice has a resonator structure, wherein a pair of semiconductordistributed-Brag-reflector mirrors (DBR mirrors) are formed on asemiconductor substrate such as GaAs or InP, and an active layerconfiguring an emission region is provided between the pair of DBRmirrors. For example, a GaAs-group VCSEL device can be formed on a GaAssubstrate, and AlGaAs-based DBR mirrors (such as including AlAs/AlGaAslayer pairs) having an excellent heat conductivity and a higherreflectance can be used. Thus, the GaAs-group VCSEL device is expectedas a promising laser device emitting a light having a wavelength rangebetween 0.8 μm and 1.0 μm. In addition, a VCSEL device including anactive layer configured by GaInAs-based materials is expected as apromising laser device which emits laser of a longer wavelength rangebetween 1.2 μm and 1.6 μm.

As a VCSEL device, an oxide-confinement-type surface-emittingsemiconductor laser device is proposed which has a structure wherein anAl-oxidized layer confines the current injection area for improving thecurrent efficiency and reducing the threshold current thereof.

With reference to FIG. 10, the configuration of a conventionalsurface-emitting semiconductor laser device used in a 850-nm-wavelengthrange and having an oxide-layer-confinement structure will be describedhereinafter. FIG. 10 is a perspective sectional view depicting theconfiguration of the conventional 850-nm-range surface-emittingsemiconductor laser device having the oxide-layer-confinement structure.The surface-emitting semiconductor laser device 100 has, on a p-typeGaAs (p-GaAs) substrate 62, a layer structure including a buffer layer63, a bottom DBR mirror 64 including 35 pairs ofp-Al_(0.9)GaAs/p-Al_(0.2)GaAs layers each having a layer thicknesscorresponding to λ/4n (λ and n are emission wavelength and refractiveindex, respectively), a lower cladding layer 66, a quantum-well activelayer 68, an upper cladding layer 70, and a top DBR mirror 72 having 25pairs of n-Al_(0.9)GaAs/n-Al_(0.2)GaAs layers each having a layerthickness corresponding to λ/4n.

In the bottom DBR mirror 64, one of the Al_(0.9)GaAs layers disposed inthe vicinity of the quantum-well active layer 68 is replaced by an AlAslayer 74, and the Al in an area of the AlAs layer 74 other than thecentral current-injection area thereof is selectively oxidized toconfigure an Al-oxidized layer 75 as the current-confinement layer. Apart of the layer structure disposed between the top portion thereof anda portion of the bottom DBR mirror is configured as a mesapost 80, onwhich a ring electrode 82 is formed. The conventional VCSEL device 10Ahaving the above structure is manufactured by a process as describedbelow.

First, semiconductor layers configuring the layer structure aredeposited using an epitaxial-growth technique. Subsequently, a portionof the layer structure disposed between the top DBR mirror 72 and aportion of the bottom DBR mirror 64 is subjected to an etching treatmentusing a photolithographic and etching process, to configure acylindrical mesapost 80 having a diameter of 30 μm, for example. In thestep of forming the mesapost 80, a configuration may be employed whereina semiconductor layer portion other than the mesapost 80 is removed byetching in its entirety, or an annular groove is formed by the etchingto configure the mesapost inside the annular groove and a peripheralarea surrounding the annular groove. The example shown in the figure issuch that the portion of the semiconductor layers other than themesapost 80 is removed by etching in its entirety.

An oxidation process is conducted wherein the layer structure configuredas the mesapost 80 is maintained in a steam atmosphere at a temperatureof about 400 degrees C., to thereby selectively oxidize the Al in theAlAs layer 74 from outside of the mesapost 80, whereby a currentconfinement layer including the Al-oxidized layer 75 is formed withinthe AlAs layer 74.

Subsequently, a SiNx passivation layer 76 is formed over the entire areaof the wafer including the top surface and side surface of the mesapost80 and a portion of the p-type bottom DBR mirror 64 near the mesapost80. Thereafter, a polyimide film 78 is formed on the entire area of thewafer by coating, followed by curing the polyimide film 78 in athree-step heat treatment wherein temperatures of 200 degrees C., 300degrees C. and 400 degrees C. are maintained for 40 minutes, 60 minutesand 60 minutes, respectively. Subsequently, a photolithographic processis conducted to remove a portion of the polyimide film 78 on the topsurface of the mesapost 80, thereby exposing the SiNx passivation layer76. The polyimide film 78, which is formed by coating to have asubstantially uniform thickness, is subjected to the influence by thecontraction etc. of the polyimide due to the post-coating heattreatment, thereby assuming a shape wherein the polyimide film ishighest at the mesapost area and gradually reduces the height in theperipheral portion.

Subsequently, an RIE system is used to etch a portion of the SiNxpassivation layer 76 exposed on the mesapost 80 by using CF gas as anetching gas, thereby forming a window for forming therethrough an n-sideelectrode. Thereafter, a metallic film is formed by evaporation to forma ring-shaped n-side electrode 82. After forming the n-side electrode82, the bottom surface of the p-GaAs substrate 62 is polished to adjustthe substrate thickness to 200 μm, followed by forming a metallic filmon the bottom surface of the substrate by evaporation to form a p-sideelectrode 86. Subsequently, an electrode anneal is conducted at ananneal temperature of 400 degrees C. for 3 minutes. After those steps asrecited above, the wafer process is finished. Subsequently, the wafer issubjected to dicing using a dicing machine to formulate devices, wherebysurface-emitting semiconductor laser devices 10A such as shown in FIG.10 can be obtained. Those devices manufactured in the manner asdescribed above are subjected to measurement tests such as for electriccharacteristics thereof, and mounted on an optical module etc. after theassembly steps. Conventional VCSEL devices are described inJP-2003-69150A1 and JP-2000-68604A1, for example.

As described above, the VCSEL device is embedded within the polyimidefilm in its entirety, and then subjected to the polishing process forthe bottom surface of the substrate, testing process and assemblyprocess, after the portion of the polyimide film on the top surface ofthe mesapost is removed. In those processes, handling of the VCSELdevice causes a contact with respect to a variety of testing equipmentsand jigs, or applies a mechanical pressure etc. thereon.

In the testing process, as shown in FIG. 11( a), a measurement probe 40is shifted on the surface of the wafer on which the mesapost 80 isformed, in order to contact the measurement probe 40 with the ringelectrode 82 of the VCSEL device. Thus, the measurement probe 40 islikely to contact the mesapost 80. In addition, as shown in FIG. 11( b),if the measurement probe 40 contacts the pad electrodes 42 which isformed on the polyimide film 78 in the peripheral area outside themesapost 80 and electrically connected to the ring electrode 82, astress caused by the measurement probe 40 is applied to the mesapost 80through the polyimide film 78.

During the polishing process for the bottom surface of the substrate, asshown in FIG. 11 (c), a portion of the top surface of the mesapost 80 ofthe VCSEL device is attached onto a polishing jig 44, and the polishingis performed in this state. In this case, the attachment of thepolishing jig 44 onto the portion configured by the bay window of themesapost 80 for emitting therethrough the laser beam is likely to causea defect on the mesapost 80. In the assembly process to the opticalmodule, the VCSEL device is likely to contact an optical fiber on thetop surface of the mesapost upon coupling thereof to the optical fiber.Further, before and after the testing process or assembly process, theVCSEL device is likely to be damaged also by a jig such as a pincetteupon holding the same by the jig.

As described above, there is a problem in the process for handling theVCSEL device that the mesapost 80 of the VCSEL device is likely to bedamaged on the surface of the mesapost 80 by a contact with respect to avariety of testing equipments or jigs due to a protruding structurethereof protruding from the peripheral area, or that the VCSEL device isdamaged on the mesapost 80 having therein the resonator structure due toa stress applied thereto.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention toimprove the conventional VCSEL device having a mesapost and therebyprovide a VCSEL device having a structure which is not likely to bemechanically damaged during the testing process or assembly processthereof on the mesapost having therein a resonator structure.

The present invention provides, in a first aspect thereof, a VCSELdevice comprising a layer structure including a top DBR mirror, a bottomDBR mirror and an active layer interposed between said top DBR mirrorand said bottom DBR mirror, a layer portion of said layer structurewhich includes at least said active layer being configured as amesapost, wherein:

a top surface of a dielectric film formed in a peripheral area disposedoutside said mesapost is located at a higher position compared to a topsurface of said mesapost.

The present invention provides, in a second aspect thereof, a VCSELdevice comprising a layer structure including a top DBR mirror, a bottomDBR mirror and an active layer interposed between said top DBR mirrorand said bottom DBR mirror, a layer portion of said layer structurewhich includes at least said active layer being configured as amesapost, a top surface of said mesapost having a mesapost terminal,said VCSEL device further comprising:

a pad terminal formed on a surface of a peripheral area disposed outsidesaid mesapost and electrically connected to said mesapost terminal, asurface of said pad terminal being located at a higher position comparedto said mesapost terminal.

Here, “a higher location” means a location which is apart from thesubstrate on which the VCSEL device is formed by a larger distance.

In accordance with the VCSEL device of the present invention, employmentof the configuration wherein the surface of the peripheral area islocated higher than the top surface of the mesapost prevents the testingequipment or handling jig from contacting with the mesapost or applyinga pressure to the mesapost to thereby damage the mesapost, duringhandling the VCSEL device in the polishing process, testing process orassembly process for the VCSEL device. Accordingly, a VCSEL devicehaving a superior reliability can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is sectional view of a VCSEL device according to a firstembodiment of the present invention.

FIG. 2 is a sectional view of a first modified example modified from theVCSEL device of FIG. 1.

FIG. 3 is a sectional view of a second modified example modified fromthe VCSEL device of FIG. 1.

FIG. 4 is a sectional view of a third modified example modified from theVCSEL device of FIG. 1.

FIG. 5 is a sectional view of a fourth modified example modified fromthe VCSEL device of FIG. 1.

FIG. 6 is a sectional view of a VCSEL device according to a secondembodiment of the present invention.

FIG. 7 is a sectional view of a VCSEL device and a laser array accordingto a third embodiment of the present invention.

FIG. 8 is a sectional view of a VCSEL device and a laser array accordingto a fourth embodiment of the present invention.

FIG. 9 is a sectional view of a VCSEL device and a laser array accordingto a fifth embodiment of the present invention.

FIG. 10 is a perspective sectional view of a conventional VCSEL device.

FIG. 11 is a view for explaining problems encountered in the polishingprocess and testing process for the conventional VCSEL device.

BEST MODES FOR IMPLEMENTING THE INVENTION

The VCSEL device of the present invention features in the first aspectthat the top surface of the dielectric film formed in the peripheralarea disposed outside the mesapost is located at a higher positioncompared to the top surface of the mesapost. The VCSEL device featuresin the second aspect thereof that the VCSEL device has a pad terminalformed on the surface of the peripheral area disposed outside themesapost and electrically connected to the said mesapost terminal,wherein the surface of the pad terminal is located at a higher positioncompared to the mesapost terminal.

The VCSEL device of the present invention is applicable to the structurewherein an annular groove is formed between the mesapost and the layerportion of the peripheral area, the annular groove having a side surfaceconfiguring a side surface of the layer portion of the mesapost.

It is a preferable embodiment of the present invention that thedielectric film has a thickness of d2 in an area between the top surfaceof the mesapost and the layer portion of the peripheral area, a maximumthickness of the dielectric film in the peripheral area is d1, and thefollowing relationship 0≦d2<d1 holds. In this case, an external stressapplied to the peripheral area is reduced during transferring to themesapost via the dielectric film, thereby protecting the mesapostagainst the external force.

In the above case, if employed, it is also preferable that thedielectric film have a thickness of d3 in another area between the areain which the dielectric film has the thickness of d2 and the top surfaceof the mesapost, and the following relationship 0≦d2<d3 holds. In thiscase, the portion of the dielectric film having a larger thickness of d3protects the sidewall etc. of the mesapost against the external force.

The dielectric film may be made of an organic resin, for example, madeof polyimide. In an alternative, the dielectric film may be made of SixNor SixOy. These different dielectric films may be layered one onanother.

The top DBR mirror may be a dielectric DBR mirror. In this case, a filmconfiguring the dielectric DBR mirror may cover the entire mesapost andconfigure a dielectric film formed in the peripheral area, or thedielectric film may cover the peripheral area.

Instead of the configuration wherein the VCSEL device is connected to anexternal electrode at the position of the ring electrode, a pad terminalconnected to the ring electrode is formed in the peripheral area, andthe pad electrode and external electrode area connected together. Inthis case, the contact or pressure occurring during connecting the VCSELdevice to the external terminal is reduced. The pad terminal may bepreferably formed on the dielectric film covering the peripheral area.

Hereinafter, embodiments of the present invention will be describedconcretely in detail with reference to accompanying drawings whileexemplifying the embodiments.

EMBODIMENT 1

FIG. 1 shows a VCSEL device according to a first embodiment of thepresent invention. In the VCSEL device 10 shown in FIG. 1, the layerstructure is formed on an n-type substrate, differently from theconventional VCSEL device 10A wherein the layer structure is formed on ap-type substrate. More specifically, the VCSEL device 10 of the presentembodiment has, on an n-GaAs substrate 12, a semiconductor layerstructure including: an n-type bottom DBR mirror including 35n-Al_(0.9)GaAs/n-Al₀₂₂GaAs layer pairs each having a thickness of λ/4nin each layer; a lower cladding layer 16, a quantum-well active layer18; an upper cladding layer 20, a confinement oxide layer comprised ofAlAs layer 24 and Al-oxide layer 25; and a p-type top DBR mirror 22including 25 p-Al_(0.9)GaAs/p-Al_(0.2)GaAs layer pairs each having athickness of λ/4n in each layer.

The central portion on the substrate surface is configured as a mesapost30. The mesapost 30 is separated from the peripheral area 54 by anannular groove which is formed in the layer structure while extendingfrom the top surface of the layer structure to a portion of the bottomDBR mirror. The width of the annular groove 52 is around 5.0 to 30 μm,whereas the height of the mesapost 54 or the depth of the annular groove52 is around 3 to 7 μm. A polyimide film 28 is formed on thesemiconductor layer structure in the peripheral area 54, wherein thelayer structure of the mesapost 30 is different from the layer structureof the peripheral area 54 only in the structure of the polyimide film28.

In the VCSEL device 10 having the above structure, the semiconductorlayer structure is deposited similarly to the conventional fabricationmethod except for the difference between the n-type and the p-type.After deposition of the semiconductor layers, the annular groove 52 isformed extending from the layer surface to a portion of the bottom DBRmirror 14 by using a photolithographic and etching process, therebyconfiguring the mesapost 30. The entire surface of the wafer on whichthe mesapost 30 is formed is coated with polyimide, which is subjectedto a needed heat treatment to form a polyimide film 28. Thereafter, aphotolithographic process is conducted to remove a portion of thepolyimide film 28 in an area corresponding to at least top surface ofthe mesapost 30 and wider than the top surface of the mesapost 30. Inthis step, the polyimide film 28 has convex and concave portions thereondue to a difference in the amount of contraction thereof depending onthe thickness of the polyimide film 28. This is likely to cause aprotruding shape on the thin polyimide film 28 in a peripheral portionsurrounding the top surface of the mesapost 30. In this case either, theheight of the surface of the polyimide film 28 in the peripheral area 54is higher than the mesapost 30 including the polyimide film 28. Afterthe etch of the polyimide film 28, p-side electrode 32 and n-sideelectrode 36 area formed on the top surface of the mesapost 30 and thebottom surface of the substrate 12, respectively.

The pad electrode 42 disposed on the peripheral area 54 is located on ahigher position compared to the position of the ring electrode 32disposed on the mesapost 30. It is to be noted here that the “higherposition” means a larger distance with respect to the surface of thesubstrate 12. The ring electrode 32 and pad electrode 42 areelectrically connected together by an evaporated metallic film formed onthe polyimide film 28, for example. Since the mesapost 30 is configuredby formation of the annular groove 52 as described heretofore, thelayers of the mesa post 30 and the layers of the peripheral area 54outside the annular groove 52 have an equal height, whereby thestructure wherein the top surface of the polyimide film 28 on theperipheral area 54 is higher than the top surface of the mesapost 30 canbe easily obtained.

The structure wherein the VCSEL device has a mesapost 30 lower than thetop surface of the polyimide film 28 reduces unnecessary contacts withrespect to the probe or jig etc. during the testing process or workingprocess such as the substrate polishing.

In the present embodiment, assuming that the maximum thickness of thepolyimide film 28 on the surface of the peripheral area 54 is d1 asshown in FIG. 1, the thickness d2 of the polyimide film 28 in thevicinity of the outer sidewall of the annular groove 52 is smaller thand1. In addition, the thickness d2 is smaller than the thickness d3 ofthe polyimide film within the annular groove 52. More specifically, thepolyimide film 28 is formed to have a large thickness d1 in the areafrom the peripheral area 54 toward the central mesapost 30, then asmaller thickness d2, and again a larger thickness d3 in the inner areadue to an increase toward the inner area. In other word, the polyimidefilm 28 has a depressed portion sandwiched between both larger-thicknessareas. Due to having such a depressed portion, the stress transferred tothe mesapost 30 is reduced when the stress is applied to the polyimidefilm in the peripheral area 54. For example, the thickness d2 of thedepressed portion of the polyimide film 28 is around 1 to 3 μm. Thethickness d1 of the polyimide film 28 in the peripheral area 54 isaround 4 to 10 μm. It is to be noted however that the surface of thepolyimide film 28 having the thickness d1 in the peripheral area 54 islocated on the higher position compared to the mesapost 30 irrespectiveof the larger thickness d3.

If the thickness d3 of the polyimide film 28 in the peripheral area isexcessively small, it is impossible to provide a sufficient differencebetween the same and the thickness d2 of the depressed portion. Inaddition, if the depressed portion has an excessively larger thickness,it is impossible to sufficiently prevent the transfer of the stress. Inthe present invention, fabrication of such a structure is easilyachieved if the vertical interval between the ring electrode 32 and thepad terminal 42 is relatively small and the conductor for communicatingtogether the ring electrode 32 and the pad terminal 42 is formed as byevaporation.

FIG. 2 shows a VCSEL device 10B according to a first modification of theabove embodiment. In this modification exemplified, a portion of thepolyimide film 28 overhanging the top surface of the mesapost 30 isremoved. The other configurations are similar to those of the embodimentof FIG. 1.

FIG. 3 shows a VCSEL device 10B according to a second modification ofthe above embodiment. In this modification exemplified, the depressedportion of the polyimide film 28 formed in the vicinity of the outerperiphery of the annular groove 52 is replaced by an area of thepolyimide film 28 having a small thickness d1 in the vicinity of theinner edge of the peripheral area 54 to thereby configure a depressedportion in the polyimide film 28. It is to be noted that d2 shown inFIG. 3 may be zero. The other configurations are similar to those in theembodiment of FIG. 1.

FIG. 4 shows a VCSEL device 10D according to a third modification of theembodiment of FIG. 1. In this modification exemplified, the polyimidefilm 28 is not formed on the top and side surfaces of the mesapost andmost of the internal of the annular groove 52, and the polyimide film 28is formed only in an outer portion of the annular groove 52.

FIG. 5 shows a VCSEL device 10E according to a fourth modification ofthe embodiment of FIG. 1. In this modification exemplified, thepolyimide film 28 is not formed on the top and side surfaces of themesapost 30 and the internal of the annular groove 52, and there is anarea in the vicinity of the inner edge of the peripheral area 54, thearea being such that the polyimide film 28 is not formed therein.

In the VCSEL devices according to the embodiment of the presentinvention and the modification, the configuration is shown wherein thetop surface of the peripheral area 54 is located at a higher positioncompared to the top surface of the mesapost 30 by using the polyimidefilm 28 as the dielectric film. However, the dielectric film is notlimited to the polyimide film, and may be other dielectric materials,and a SixN film or SixOy film may be formed in the peripheral area tohave a larger height compared to the mesapost.

EMBODIMENT 2

FIG. 6 shows a VCSEL device according to a second embodiment of thepresent invention. In the present embodiment, a resin lens 38 is formedon the top surface of the mesapost of the VCSEL device of the embodimentshown in FIG. 1. The resin lens 38 is formed on the surface of thepolyimide film 28 overlying the mesapost 30 and the annular groove 52 bytaking advantage of the depressed shape of the polyimide film 28,configuring a domed top surface. In the present embodiment, the size ofthe depressed portion of the polyimide film 28 is appropriatelyselected, to allow a suitable size of the resin lens 38 to be easilyobtained, without the necessity of alignment of the VCSEL device withrespect to the lens. In addition, formation of the resin lens 30directly on the mesapost 30 allows the optical system, which opticallycouples the VCSEL device with an optical fiber, to be formed in asmaller size, and obtains a function of protecting the top surface ofthe mesapost 30 by the resin lens 30.

The structure of the VCSEL device of the present invention is applicableto a laser array, in which VCSEL devices are arranged in atwo-dimensional array on a common substrate for integration. Inparticular, the configuration of the VCSEL device of the presentinvention reduces the damage incurred in the polishing process, testingprocess etc., thereby providing a higher reliability which is generallyrequired for all the plurality of VCSEL devices integrated

EMBODIMENT 3

FIGS. 7( a) and (b) are side views respectively showing a VCSEL device10G according to a third embodiment of the present invention and a laserarray 50 wherein such VCSEL devices 10G are arranged in atwo-dimensional array on a common substrate for integration. As depictedin FIG. 7( a), in the VCSEL device 10G of the present embodiment, thetop DBR mirror is configured as a dielectric DBR mirror 46, and theentire surface of the mesapost 30 and dielectric film 28 is covered by afilm configuring the dielectric DBR mirror 46 to obtain the structure.

On a semi-insulating substrate 13 is formed a bottom DBR mirrorconfigured by semiconductor layers, on which an n-type lower claddinglayer 56, active layer 18 and a p-type semiconductor cladding layer 58are formed, wherein these lower cladding layer 56, active layer 18 andupper cladding layer 58 are left as a layer portion in the peripheralarea. A dielectric film 28 made of polyimide is formed to cover thislayer portion in the peripheral area, and the dielectric film 28 iscovered by a film configuring the dielectric DBR mirror 46. The surfaceof the peripheral area is formed to be higher than the top surface ofthe mesapost 30. The dielectric DBR mirror 46 is configured by a layerstructure including a plurality of pairs each including an amorphoussilicon and a silicon oxide in pair, or a layer structure including aplurality of pairs each including a silicon oxide film and a siliconnitride film in pair.

In the mesapost 30, an n-side electrode 36A is formed on a surfaceportion of the lower cladding layer 56, and is connected to the n-sidepad electrode 48 formed on the film configuring the DBR mirror 46 in theperipheral area. Similarly, the p-side electrode 32 configuring the ringelectrode is connected to the p-side electrode 42 formed on the filmconfiguring the DBR mirror 46 in the peripheral area. These padelectrodes 42, 48 are made from an Au film, for example.

As shown in FIG. 7( b), a large number of VCSEL devices 10G having theabove configuration are formed on a common substrate 12 to configure thelaser array 50. Due to the peripheral area of the VCSEL devices beinghigher the mesapost 30, and also due to the dielectric DBR mirror 46covering the entire device, damage applied to each of the laser devicesis reduced during the polishing process, testing process etc.

EMBODIMENT 4

FIG. 8 shows a VCSEL device 10H according to a fourth embodiment of thepresent invention and a laser array 50A, similarly to FIG. 7. The VCSELdevice 10H of the present embodiment is different from the VCSEL device10G of the third embodiment in that the layer portion of the peripheralarea is entirely removed in the present embodiment. The dielectric film28 such as polyimide is formed to have a larger thickness in the layerportion thus removed. The laser array 50A is such that a larger numberof VCSEL devices having the above structure are disposed on a commonsubstrate 12.

EMBODIMENT 5

FIG. 9 shows a VCSEL device 10I according to a fifth embodiment of thepresent invention and a laser array 50B, similarly to FIG. 7. The VCSELdevice 10I of the present embodiment is different from the VCSEL device10G of the embodiment shown in FIG. 8 in that the film configuring thedielectric DBR mirror 46 is covered by the dielectric film 28 such aspolyimide formed in the peripheral area. The dielectric DBR mirror 46 isformed to cover the entire surface of the mesapost 30. The n-side padelectrode 48 and p-side pad electrode 42 are formed on a surface portionof the dielectric film 28.

It is to be noted that although VCSEL device and laser array formed onan n-type substrate are exemplified in the above embodiments, thesubstrate used may be any of n-type and p-type ones, and that the p-typeand n-type are reversed from the above embodiments if the VCSEL deviceis formed on the p-type substrate.

Although the present invention is described with reference to thepreferred embodiments, the VCSEL device of the present invention is notlimited to the above embodiments, and a variety of modifications oralterations from the above embodiments will fall within the scope of thepresent invention.

1. A surface-emitting laser (VCSEL) device comprising a layer structureincluding a top DBR mirror, a bottom DBR mirror and an active layerinterposed between said top DBR mirror and said bottom DBR mirror, alayer portion of said layer structure which includes at least saidactive layer being configured as a mesapost, wherein: a top surface of adielectric film formed in a peripheral area disposed outside saidmesapost is located at a higher position compared to a top surface ofsaid mesapost.